Oncosuppressive gene

ABSTRACT

Isolation and characterization of an oncosuppressive gene which is involved in the apoptotic process and is regulated by p53 ad p73, polypeptide thereby encoded, sequences involved in gene regulation and genetic constructs thereof.

CROSS REFERENCE TO RELATED APPLICATION

This application is a 35 U.S.C. § 371 National Phase Entry Application from PCT/EP02/07625, filed Jul. 9, 2002, and designating the U.S.

The present invention regards the isolation and characterization of a novel gene which is involved in programmed cell-death (apoptosis) and has oncosuppressive activity. The gene is regulated by p53 and p73, which are known to activate the transcription of genes involved in cell-cycle block and apoptosis. p73 and p53 have homologous sequences, especially in the central region including the DNA-binding domain, and share a common pattern of gene-activation. However, their oncosuppressive activities, in particular the pro-apoptotic effects, are not completely clarified. Therefore the search of genes activated by p53 and p73 attracts a great scientific and applicative interest.

PRIOR ART

Nagase et al., DNA Research 3, 321–329 (1996), reports the sequencing of human cDNA clones obtained from a library of human cDNAs, and the predicted coding sequences of 80 new genes (KIAA0201 to KIAA0280) deduced by analysis of cDNA clones. The coding sequence named KIAA0247 is present in the gene isolated according to this invention. The referenced publication does not contain information as to the structure and function of the gene.

WO01/18542 lists a huge number of cDNA sequences identified by subtraction library construction, which are overexpressed in ovarian tumor cells and hence proposed for use as ovarian cancer markers. Sequence n. 1.18 shows high homology with the coding sequence of the present gene.

DESCRIPTION OF INVENTION

In differential-display experiments with human ovarian carcinoma cells A2780, a cDNA fragment whose expression increased after treating the cells with a synthetic derivative of distamycin A was identified. This compound is known to interact with the DNA minor groove.

The same effect was observed with cytotoxic compounds differing from distamycin A by their mechanism of action, such as cisplatin, taxol, doxorubicin and fluorouracil; obtaining in each case an increased production of the same fragment.

To verify whether the increase was mediated by p53, the effects of antitumnor drugs were evaluated in isogenic model-systems differing for p53 expression. An increased transcription of the isolated cDNA could not be observed in cells where the p53 gene had been inactivated, suggesting that the activity of the gene under investigation is regulated by p53.

The complete cDNA containing the isolated fragment was then isolated from a cDNA-library and entirely sequenced. It has 5338 base pairs (SEQ ID N. 1) and codes for a protein of 303 amino acids (SEQ ID N. 2). The coding region spans nucleotides 269 to 1177 (1180, including the stop codon “tga”), while nucleotides 1180–5338, which form the non-translated 3′ region (SEQ ID N. 3), are involved in the regulation of protein synthesis by controlling the stability of the corresponding transcript.

In a first embodiment the invention is directed to a DNA molecule having sequence SEQ ID No. 1. In a further embodiment the invention provides SEQ ID N. 3, which is the sequence complementary to the non-translated mRNA region involved in the regulation of protein synthesis.

Included within the scope of the invention are also nucleic acid molecules, their stable analogs or mimetics, such as PNA (Peptide Nucleic Acid) molecules, or other derivatives thereof that do not undergo in vivo degradation or biotransformation, which can hybridize to the DNA molecule of SEQ ID No. 3, or to a complementary sequence thereof. Such products can be used to modulate the function of the regulatory sequence contained in the transcript of the isolated gene. As herein used, the term “hybridization” may refer to stringent or non-stringent conditions. These can be easily determined by anyone skilled in the art following known protocols (see for example Sambrook, “Molecular Cloning, A Laboratory Manual”, Cold Spring Harbor Laboratory, N.Y. (1989), or Ausbel, “Current Protocols In Molecular Biology”, Green Publishing Associates and Wiley Interscience, N.Y. (1989)).

The protein encoded by the complete cDNA was biochemically characterized. It showed a molecular weight, calculated by SDS-PAGE, of 30–35 kDa, consistent with the number of amino acids (303) deducible from the sequence. To determine its cellular location, fusion proteins were prepared from constructs combining the isolated c-DNA sequence with sequences coding for proteins or protein fragments detectable by microscopy, such as HA, FLAG or GFP. In these experiments the cells were transiently transfected and examined at different times. The expression product bearing the GFP protein was found to locate within cell vesicles and membranes. The same location was observed in different human and murine cell lines. Further, morphologic changes following gene overexpression were evaluated in transiently transfected cells. Several cytoplasmic vacuoles were present in cells transfected with the GFP-cDNA construct. In some cases the cell membranes appeared disrupted and the vacuole content was extra-cellularly released. The same effects were previously reported for apoptotic cell lines other than those of type II (where nuclear fragmentation occurs).

According to a further aspect, the invention is directed to the polypeptide SEQ ID N. 2 and to its DNA coding sequence SEQ ID N. 4. Included are also sequence variants of the polypeptide SEQ ID N. 2, due to substitution, addition or deletion of one or more amino acids, provided that its specific functions are maintained. As to the deletion variants, peptides generated by repeated deletions at the N-terminus of SEQ ID N. 2 showed an activity similar to that of the parent polypeptide. In particular, (poly)peptides 12-303, 23–303, 35–303, 49–303, 60–303 and 74–303 (referred to nucleotide positions in SEQ ID N. 2), which were found to maintain the same oncosoppressive activity as the parent polypeptide, represent a further object of the invention.

Using the information available with the fall-length cDNA, the structure of the human oncosuppressive gene (DRAGO) was molecularly characterized. It consists of 6 exons, the first of which (188 bp) forming the non-translated 5′ region. Exons 2,3,4 and 5 (201, 198, 140 and 427 bp respectively) correspond to the coding region which contains the first 26 bases of exon 6 (4184 bp) and additionally the entire non-translated 3′, region. Interestingly, the gene presents two large introns (45–50 kb) between exons 1–2 and 2–3, respectively. The presence of such introns, and of the large untranslated region as well, implies a strong gene regulation. Starting from a 10735 bp region located upstream of the first exon (SEQ ID N. 5), a 3761 bp fragment (SEQ ID N. 6), consisting of the first intron, the first exon and a sequence portion contiguous to exon-1 5′-end, was isolated. This fragment was functionally linked to a reporter gene (luciferase) to determine its transcription promoter activity. In p53-defective cells, a sustained transcription of the reporter gene could be detected. In cells where p53 functionality had been restored by co-transfection of a vector carrying the p53 gene under the control of a strong viral promoter, the promoter activity of the 3761 fragment was two-fold increased. This result is consistent with the experiments conducted in isogenic p53⁺ or p53⁻ model-systems. The observed p53 regulation is similar to that of other p53-responsive promoters such as the p21-gene promoter.

An even stronger promoter activity in response to p73 and p53 was observed with fragments of the 3761 bp sequence. In experiments where cells were co-transfected with DNA fragments—SEQ ID. No. 9 to 15—subcloned upstream of the luciferase gene and with either p73- or p53-encoding plasmids, a high expression of the reporter was found.

Sequences SEQ ID N. 5–6 and 9–15, which are endowed with transcription promoter activity responsive to p53 and p73, are embodiments of this invention. They can be used in the preparation of gene constructs and vectors useful for the study of oncosuppressive-gene expression. In particular these sequences, as well as the untranslated regulatory sequence of SEQ ID N. 3, can be used for the screening of compounds that modulate the expression of the oncosuppressive product. In a typical assay, the candidate compound is incubated with cells transfected with the regulatory sequences operatively linked to a suitable reporter gene, and then the ability of the e compound to modulate the expression of the reporter gene and/or to modify particular cell functions or properties, such as their growth in response to particular stimuli, is determined. Moreover, animals transgenic for the same sequences can be produced. In a further application, animal models carrying particular tumors can be used to study the ability of candidate compounds to modulate the expression of the oncosuppressive gene.

The murine oncosuppressive gene was also cloned and resulted highly homologous to the human gene, with a nucleotide (SEQ ID N. 7) and amino acid (SEQ ID N. 8) identity of 87% and 88%, respectively.

The identification of murine gene sequences enables the preparation of knock-out mice. A suitable strategy can be summarized as follows. Initially, a region of the gene of approx. 6–7 kb, preferably containing the exons 3–5, after insertion in a suitable vector, is partially replaced by a gene conferring antibiotic resistance, such as the neomycin-resistance gene, which, besides functioning as selection marker, causes inactivation of the oncosuppressive gene by interrupting its transcription.

ES cells are then transfected with the recombinant construct and only those keeping viable and growing in a medium added with the antibiotic are selected. The positive clones are then identified by PCR and Southern blot and introduced into blastocysts by microinjection. The thus generated chimera mice are initially heterozygous (−/+) and then, after breeding, homozygous (−/−) for the inactivated gene.

DESCRIPTION OF THE FIGURES

FIG. 1. Differential display analysis of gene expression in A2780 cells untreated or treated with a distamycin derivative for 1 hour. The RNA was extracted 1, 6 or 24 hours after treatment.

FIG. 2. Northern blot confirming the increased expression of fragment 1 mRNA (FIG. 1).

FIG. 3. RT-PCR analysis of the isolated-cDNA expression in control cells (C) and in cells treated with cisplatin (DDP).

FIG. 4. SDS PAGE—the protein produced in vitro from the isolated cDNA is indicated by an arrow. Gel stained with Coomassie Blue.

FIG. 5. Staining of A2780 colonies recovered after transfection with a control vector (pCDNA3) or with a vector containing the isolated cDNA.

FIG. 6. RT-PCR analysis of the isolated-cDNA expression in murine embryonic fibroblasts from wild-type mice (+/+) or p53 (−/−) knock-out mice, treated or not with the distamycin derivative for 1 hour. The RNA was extracted 1, 6 or 24 hours after treatment.

FIG. 7. RT-PCR analysis of isolated-cDNA expression in HCT116 cells expressing wild-type. p53 (+/+) or in HCT116 cells p53-inactivated by homologous recombination (−/−), treated or not (Controls) with the. distamycin-A derivative for 1 hour. The RNA was extracted 1, 6 or 24 hours after treatment.

FIG. 8. Molecular structure of the gene, indicating the number of base pairs of each exon.

FIG. 9. Transcription-promoter activity of a 3761 bp fragment containing the first intron, the first exon and the region contiguous to the 5′-end of the first exon. The fragment was subcloned upstream of the luciferase gene and co-transfected with p53-expressing or p53-defective vectors. p21 promoter was used as control for the p53-responsive control gene. Sub-cloning vector: PGL2.

FIG. 10. Transcription-promoter activity of 2.5 Kb fragment linked to luciferase gene was evaluated in p53 (−/−) Saos-2 cells in cotransfection experiments with p73 different isoforms and p53. Activation of 2.5 Kb lo fragment was compared with p21 promoter.

FIG. 11. DN-p73 repression of transcription activity of p73α and p73γ on p21-luciferase promoter. Increasing concentration of DN-p73 was used in co-transfection experiments with p73α and p73γ.

FIG. 12. DN-p73 cooperation with p73α, p73β, p73γ, p73δ in transactivation of 2.5 Kb fragment-luciferase construct with increasing concentrations of DN-p73. The first column shows induction of 2.5 Kb fragment by DN-p73 alone.

FIG. 13. Response of 3761 bp fragment and deleted mutants to p53 and p73α, p73β, p73γ, p73δ. Fragments were subcloned upstream to the luciferase gene. (the sequences of fragments 2.5 KB, SmaI, PstI(a)+PstI(b), PH3, HP4, SP5 and 964 bp are respectively reported in SEQ ID N.: 9, 10, 12+13, 11, 14, 15, 16)

EXAMPLES Example 1 Isolation and Characterization of the Human cDNA

Human ovary carcinoma A2780 cells were treated for 1 hour with an antitumor derivative of distamycin-A at its 50% growth-inhibiting concentration; at the end of the treatment and after 6 and 24 hours the total RNA was isolated by column extraction (SVTotal RNA, Promega Italia) and reverse-transcribed using poly-T primers as indicated in the differential-display kit (GenHunter). The fragments thus obtained were separated on denaturing polyacrylamide gel and detected by autoradiography. The bands whose intensity differed from controls were isolated and purified. One of them (fragment 1), after purification and ³²P-labeling (rediprime kit, Amersham), was used as probe in Northern Blot experiments. The RNA from the same cells was separated on agarose gel, transferred onto nylon membrane and hybridized with the probe.

To isolate the complete cDNA containing fragment 1, a cDNA library

Human ovary carcinoma A2780 cells were treated for 1 hour with an prepared from human fibroblasts using λgt10 vector was hybridized with the probe (see “Molecular Cloning, A Laboratory Manual”, Cold Spring Harbor Laboratory, N.Y. (1989), or Ausbel, “Current Protocols In Molecular Biology”, Green Publishing Associates and Wiley Interscience, N.Y. (1989)). The positive clones were isolated, sequenced and the full-length cDNA (5338 bp) was cloned in pBluescript vector (Stratagene). The coding region results comprised between nucleotides 269 and 1177 (1180 including the stop codon “tga”) whereas the remaining 4158 nucleotides form the non-translated 3′ region.

Example 2 Analysis of cDNA Expression in Cells Treated with Different Cytotoxic Agents

PCR experiments using oligonucleotides derived from the isolated cDNA evidenced an increase of mRNA production in cells treated with different antitumor compounds other than distamycin and having a different mechanism of action with respect to the latter, such as cisplatin and taxol, which cause DNA damage and microtubule stabilization, respectively.

Cells A2780 were treated with taxol and cisplatin (DDP) and the RNA was extracted before and 24 hours after the treatment. The amount of specific mRNA was determined by PCR following reverse-transcription of the total RNA (1 μg) with primers derived from the coding region of fragment 1 (5′-ctcgagtgccatggcaggatagcacc [SEQ ID NO: 17] and 5′-tctagatcatgcttctttcaacagtg [SEQ ID NO: 18]), according to the protocol supplied in the RNA-PCR kit (Perkin Elmer). The amplified fragment (923 bp) was separated on agarose gel. A fragment of beta-actin gene was used as internal control. FIG. 3 shows the results obtained treating the cells with cisplatin (DDP): the band associated with the isolated gene is more intense than that of control cells (C) in conditions in which the levels of beta-actin gene are comparable in the two groups. Similar results were obtained using taxol and other antitumor drugs.

Example 3 Protein Characterization and Intracellular Location

Using the isolated full-length cDNA as template, a polypeptide was produced (Promega TNT express kit) with an apparent molecular weight, calculated by SDS-PAGE, of 30–35 kDa (FIG. 4). This mol weight is consistent with the structure of the polypeptide and with the number of amino acids (303) deducible from its sequence (SEQ ID N. 2).

Transient transfection experiments were conducted to determine the intracellular location of the polypeptide. To this end, the latter was fused to proteins or protein fragments such as HA or FLAG, which can be detected by microscopy using fluorescent antibodies, or GFP, which is an intrinsically fluorescent protein. In these experiments the cells were analyzed 24 and 48 hrs after transfection with different constructs. Using a GFP-construct, the polypeptide was found to localize within cellular vesicles and membranous structures. Under the same conditions, as expected, GFP alone was uniformly located within the cell. The same effects were observed in different human and murine cell lines.

Transient transfection experiments were also conducted to assess morphologic modifications occurring 24 and 48 hrs after gene overexpression. Cells transiently transfected with a GFP construct showed in all cases the presence of several cytoplasmic vacuoles, less frequently the membrane appeared disrupted and the vacuole content released in the extracellular areas. Transfection with GFP alone was not associated with any evident morphologic alteration.

Example 4 Effects of Gene Overexpression in Eukaryotic Cells

The effects of gene overexpression were evaluated in cells carrying constructs in which the isolated cDNA was functionally linked to a strong viral promoter.

The complete cDNA (5338 bp) and the coding region (nucleotides 1–1180) were used for vector assembly. The two sequences were excised from pBS plasmid (Stratagene) and inserted into pCDNA3 (Invitrogen), pCDNA3-HA and pCDNA3-FLAG expression vectors. These two latter were prepared from pCDNA3 by insertion of the HA and FLAG coding sequences. The coding portion of the isolated cDNA was amplified by PCR (primers: 5′-ctcgagtgcatggcaggatagcacc [SEQ ID NO: 19] and 5′-tctagatcatgcttctttcaacagtg [SEQ ID NO: 18]) and sub-cloned in frame with the HA and FLAG sequences. Similar constructs were prepared from GFP (green fluorescent protein). In this case, the coding sequence of the isolated cDNA was subcloned in frame with the GFP cDNA in a pEGFP-C1 vector (Clontech). Each construct was automatically sequenced to verify its correct assembly and transfected into A2780 cells by calcium phosphate precipitation, according to the following procedure. 5–10 micrograms of plasmidic DNA were mixed with calcium chloride and phosphate buffer to form fine calcium phosphate precipitates, and this mixture was applied to a cell culture (70% confluence) for a period of 12–16 hrs. The cells were rinsed with PBS, rested for 48 hrs, counted and plated (5000 cells/10 cm plate) in a culture medium added with neomycin. 15 days later the culture medium was removed and the colonies dyed with crystal violet, washed and photographed. FIG. 5 shows the photograph of a plate in which A2780 cells were transfected with the isolated cDNA or with vector pCDNA3 alone. No colonies could be detected in cDNA-bearing cells, whereas several colonies were present in the culture treated with vector alone. The overexpression of the complete cDNA (5338 bp) or its 1180 bp fragment (coding region) prevented colony formation. This effect was observed in A2780 cells (ovary carcinoma), SaoS2 and U2OS lines (human osteosarcoma), and 3T3 lines (murine fibroblasts). Failure to isolate stable clones was due to the strong growth-suppressing effect following gene-overexpression.

Example 5 Role of p53 in Gene Activation

To ascertain whether the activity of the gene was mediated by p53, the effects of antitumor drugs in isogenic models with different p53 expression were examined. No expression was found in embryonic fibroblasts from p53 knock-out mice (FIG. 6). In these experiments, fibroblasts from wild-type and p53 knock-out mice were treated with a distamycin derivative for 1 hour. The RNA isolated 1, 6 and 24 hours after the treatment was used to amplify a cDNA containing the coding portion of the murine gene (primers: 5′-ctcgagtgccatggcaggatagcacc [SEQ ID NO: 17] and 5′-tctagatcatgcttctttcaacagtg [SEQ ID NO: 18]). The antitumor compound failed to induce gene expression in a HCT116 clone where p53 had been inactivated by homologous recombination (HCT116 p53 −/−); in contrast, gene expression was observed in the parental cell line (FIG. 7). The same conditions as in the experiments with embryonic fibroblasts were used. These results demonstrate that p53 is necessary for gene activation.

Example 6 Molecular Characterization of the Human Gene

A pCYPAC2-subcloned PAC RPCI1 genomic library from the UK Human Genome Mapping Project Resource Center was used (Hinxton, UK). This library was established from the blood of a healthy subject and consisted of approx. 120000 clones spotted in duplicate on 7 membrane filters (22.2 ×22.2 cm). A 5′-fragment (160bp) generated by PCR (primers: 5′-ctcgagtgccatggcaggatagcacc [SEQ ID NO:17] and 5′-tctagatcatgcttctttcaacagtg [SEQ ID NO: 18]) was used as hybridization probe. The latter was ³²P-labeled and incubated with the filters for 16 hrs. After extensive washing, the filters were exposed to an autoradiographic film. Two positive clones (92D20 and 67A24) were identified and the genomic DNA of one of them was partially sequenced (terminal regions). Using sequence information available from a database, the structure of the gene was defined.

Example 7 Role of p53 in Gene Transcription

The region (10735 bp—SEQ ID N. 5) located upstream of the first exon was isolated from one PAC clone. A portion of it (3761 bp), containing the first intron (partially), the first exon and a region adjacent to the 5′-end of exon 1, was sub-cloned in pGL2 vector (Promega) upstream of the luciferase gene. A significant transcription of the reporter gene was detected with a luninometer 48 hrs after transfection of semi-confluent p53⁻ cells with the construct (10 μg). Cells transfected with pGL2 vector alone (without the 3761 bp fragment) were used as the control.

In co-transfection experiments, the cells were transfected with both the same construct and an expression vector containing the entire p53 gene under the control of a strong viral promoter. In the presence of p53, the isolated fragment (3761 bp) induced a transcription of the reporter gene two fold higher than in its absence, which is consistent with the results of the experiments carried out in isogenic models differing for p53 expression (FIG. 9).

Example 8 Role of p73 in Gene Transcription

Different isoforms of p73 are generated by alternative splicing of p73 gene. The full length protein is defined as alpha p73 and at least 4 isoforms (beta, gamma, delta and epsilon) have been described so far. These isoforms can have different transcriptional activation potency. An additional, truncated form of p73 lacking the first 3 exons has been described. This form, named DNp73, does not result from a different splicing, but utilizes an additional promoter, positioned between exons 3 and 4 of the wt protein. The DNp73 protein has been shown to bind DNA but is not able to activate transcription for lack of the transactivation domain.

Experiments were carried out in which the 3761 bp fragment (SEQ ID n. 6) was subcloned in the pGL2 vector upstream of the luciferase gene and used to determine p73-dependent gene transcription. A further deletion of SEQ ID N. 6 generated a fragment of 2.5 Kb (SEQ ID N. 9) that was used to test the specific activity of different p73 isoforms.

Cells were co-transfected with the pGL2-derived construct and with expression plasmids containing the full-length regions coding for p53 and for different p73 isoforms. 48 hours after transfection, cells were lysed and the luciferase activity measured by standard, commercially available kits (Promega).

A typical experiment is reported in FIG. (10), showing the ability of p53 and of different p73 isoforms to activate the promoter region (single experiment).

p73 is a stronger activator of the promoter fragment than p53. Among different p73 isoforms, beta and gamma isoforms are the strongest.

To test the ability of DN-p73 to block p73-induced transactivation, we have conducted experiments in which the promoter-luciferase construct has been cotransfected with the expression plasmid. As a control we have used the p21-luciferase construct. As expected, increasing the amount of DNp73, transactivation of p21 promoter by p73 tends to decrease (FIG. 11). With 2.5 Kb fragment-pGL2 construct, increasing amounts of DNp73 determined a concentration-dependent increase of luciferase activity, which suggests a cooperation between p73 and DNp73 in transactivating this DNA sequence. DNp73 is also able to transactivate 2.5 Kb fragment-luciferase construct when transfected in the absence of p53 or p73. This effect is not observed with the p21 promoter sequence (FIG. 12)

Example 9 Fragments Retaining Promoter Activity

Fragments of the 3761 bp DNA were generated (FIG. 13). These fragments, subcloned upstream to the luciferase gene, have been co-transfected with p73 and p53 expressing plasmids in an attempt to restrict the DNA region responsible for the p53- and p73-dependent transactivation.

In FIG. 13 the luciferase activities are reported. The sequence of 2.5Kb results particularly responsive to p73.

The fragment of 964 bp (SEQ ID N. 16) does not respond to any of the p73 isoforms nor to p53. Further deletions of the 3761 bp sequence retain a promoter activity responsive to p73, particularly to the beta and gamma isoforms, while the p53-dependent luciferase activity was almost abolished. The SP5 fragment (577 base pairs) is particularly responsive to p73 gamma.

Example 10 Isolation of Murine cDNA

In consideration of the high oncosuppressive effect exerted by the isolated gene, its murine homologue was cloned via PCR using primers derived from the human sequence. The identity was 87% for the nucleotide sequence and 88% for the amino acid sequence (SEQ ID N. 7-8, respectively).

The RNA from 3T3 murine fibroblasts was reverse-transcribed (random hexamers- RNA PCR kit Perkin Elmer) and used for the amplification of a 909bp fragment (primers 5′-ctcgagtgccatggcaggatagcacc [SEQ ID NO:17] and 5′-tctagatcatgcttctttcaacagtg [SEQ ID NO:18])

The isolated fragment (nt 1-906; the terminal “tga” is a stop codon) codes for a 302 aa polypeptide (i.e. 1 aa less than the corresponding human polypeptide). 

1. An isolated DNA molecule selected from the group consisting of SEQ ID NOS:5, 6, 9, 10, 11, 14, 15, and a construct comprising, from 5′ to 3′, SEQ ID NO:12 and SEQ ID NO:13, which when operably associated with a gene, regulates expression of that gene.
 2. An isolated DNA molecule according to claim 1, having transcription promoter activity responsive to p53, and comprising SEQ ID NOS:5, 6, or
 9. 3. An isolated DNA molecule according to claim 1, having transcription promoter activity responsive to p73, which is selected from the group consisting of SEQ ID NOS:5, 6, 9, 10, 11, 14, 15, and a construct comprising, from 5′to 3′, SEQ ID NO:12 and SEQ ID NO:13.
 4. A genetic construct, comprising a sequence selected from the group consisting of SEQ ID NOS: 5,6, 9, 10, 11, 14, 15, and a construct comprising, from 5′ to 3′, SEQ ID NO: 12 and SEQ ID NO: 13, wherein the sequence is operably linked to a reporter gene, and wherein the sequence regulates expression of said reporter gene. 